Thymoquinone suppresses invasion and metastasis in bladder cancer cells by reversing EMT through the Wnt/β-catenin signaling pathway

Epithelial mesenchymal transformation plays a crucial role in the metastasis of bladder cancer, which makes bladder cancer difficult to cure. Bladder cancer is the most common malignancy of the urinary system, and distant metastasis is the leading cause of death. Therefore, finding a bioactive drug that can specifically inhibit epithelial mesenchymal transformation may be a new direction for bladder cancer treatment in the future. Thymoquinone (TQ), the major active compound isolated from black seed oil (Nigella sativa), has been reported to exhibit anti-inflammatory and anticancer abilities. TQ can exhibit its antitumor effect by inhibiting the proliferation and metastasis of cancer cells. However, the underlying mechanism of TQ as a tumor inhibitor in bladder cancer remains poorly understood. First, in this research, we demonstrate that TQ can reverse EMT by upregulating epithelial markers, such as E-cadherin, and downregulating mesenchymal markers, such as N-cadherin and vimentin. Furthermore, we demonstrate that TQ can suppress the activation of the Wnt/β-catenin signaling pathway and inhibit the expression of β-catenin target genes, such as MYC, Axin-2, MMP7, CyclinD1 and MET, which play crucial roles in EMT and cancer progression. Additionally, we demonstrate that TQ can inhibit the growth of xenografts and restrict the formation of tumor metastatic foci in the lung. Taken together, our findings confirm the antimetastatic effect of TQ in bladder cancer cells for the first time and also provide new evidence for the development of TQ as a novel treatment for metastatic bladder cancer.